WO2011062081A1 - Film de polyester diffusant la lumière - Google Patents

Film de polyester diffusant la lumière Download PDF

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Publication number
WO2011062081A1
WO2011062081A1 PCT/JP2010/069887 JP2010069887W WO2011062081A1 WO 2011062081 A1 WO2011062081 A1 WO 2011062081A1 JP 2010069887 W JP2010069887 W JP 2010069887W WO 2011062081 A1 WO2011062081 A1 WO 2011062081A1
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WO
WIPO (PCT)
Prior art keywords
light
layer
film
polyester
polyester film
Prior art date
Application number
PCT/JP2010/069887
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English (en)
Japanese (ja)
Inventor
芳紀 斎宮
西　睦夫
Original Assignee
東洋紡績株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2009265023A external-priority patent/JP5696356B2/ja
Application filed by 東洋紡績株式会社 filed Critical 東洋紡績株式会社
Publication of WO2011062081A1 publication Critical patent/WO2011062081A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/023—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets using multilayered plates or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
    • B29C48/07—Flat, e.g. panels
    • B29C48/08—Flat, e.g. panels flexible, e.g. films
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/91—Heating, e.g. for cross linking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/88—Thermal treatment of the stream of extruded material, e.g. cooling
    • B29C48/911—Cooling
    • B29C48/9135—Cooling of flat articles, e.g. using specially adapted supporting means
    • B29C48/914—Cooling of flat articles, e.g. using specially adapted supporting means cooling drums
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/36—Layered products comprising a layer of synthetic resin comprising polyesters
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92504—Controlled parameter
    • B29C2948/92704—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C2948/00—Indexing scheme relating to extrusion moulding
    • B29C2948/92—Measuring, controlling or regulating
    • B29C2948/92819—Location or phase of control
    • B29C2948/92857—Extrusion unit
    • B29C2948/92904—Die; Nozzle zone
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/001—Combinations of extrusion moulding with other shaping operations
    • B29C48/0018—Combinations of extrusion moulding with other shaping operations combined with shaping by orienting, stretching or shrinking, e.g. film blowing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/16—Articles comprising two or more components, e.g. co-extruded layers
    • B29C48/18—Articles comprising two or more components, e.g. co-extruded layers the components being layers
    • B29C48/21—Articles comprising two or more components, e.g. co-extruded layers the components being layers the layers being joined at their surfaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/30—Extrusion nozzles or dies
    • B29C48/305—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets
    • B29C48/307—Extrusion nozzles or dies having a wide opening, e.g. for forming sheets specially adapted for bringing together components, e.g. melts within the die
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/375—Plasticisers, homogenisers or feeders comprising two or more stages
    • B29C48/387—Plasticisers, homogenisers or feeders comprising two or more stages using a screw extruder and a gear pump
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
    • B29C48/25—Component parts, details or accessories; Auxiliary operations
    • B29C48/36—Means for plasticising or homogenising the moulding material or forcing it through the nozzle or die
    • B29C48/50—Details of extruders
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C55/00—Shaping by stretching, e.g. drawing through a die; Apparatus therefor
    • B29C55/02—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets
    • B29C55/10—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial
    • B29C55/12—Shaping by stretching, e.g. drawing through a die; Apparatus therefor of plates or sheets multiaxial biaxial
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2067/00—Use of polyesters or derivatives thereof, as moulding material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
    • B29K2995/00—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds
    • B29K2995/0018—Properties of moulding materials, reinforcements, fillers, preformed parts or moulds having particular optical properties, e.g. fluorescent or phosphorescent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2007/00—Flat articles, e.g. films or sheets
    • B29L2007/008—Wide strips, e.g. films, webs
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2031/00—Other particular articles
    • B29L2031/764—Photographic equipment or accessories
    • B29L2031/7644—Films

Definitions

  • the present invention relates to a light diffusing film used for a backlight unit of a liquid crystal display, an illumination device, and the like. More specifically, the present invention relates to a light diffusible polyester film that achieves both light diffusibility and light transmittance and does not cause curling during high-temperature treatment.
  • liquid crystal displays In recent years, technological advances in liquid crystal displays have been remarkable, and they are widely used as display devices for personal computers, televisions, mobile phones and the like. In particular, in recent years, high definition has been advanced for various uses of liquid crystal displays. Especially for television applications, with the widespread use of high-definition broadcasting, horizontal 1920 ⁇ vertical 1080 dots, which has traditionally been mainly used for large-screen liquid crystal televisions. The so-called full HD display liquid crystal panel has been adopted for a relatively small screen size LCD TV, and the demand for higher definition is increasing. Since these liquid crystal displays do not have a light emitting function by themselves, a liquid crystal display unit can be displayed by installing a backlight unit on the back surface thereof.
  • the backlight unit includes a direct type in which a light source is installed inside the illumination surface, and an edge light type in which light is introduced from the outside of the illumination surface through a light guide plate.
  • These backlight units are further provided with a light diffusing film, and are devised to diffuse and scatter light to make the luminance of the illumination surface uniform.
  • a sheet having a light collecting function called a lens sheet may be used so that light transmitted through the light diffusing film is collected in the front direction as much as possible.
  • the surface of the sheet has a large number of minute irregularities such as a prism shape, a wave shape, and a pyramid shape, and the emitted light that has passed through the light diffusing film is refracted and collected in the front to improve the luminance of the illumination surface.
  • a lens sheet is disposed and used on the surface side of the light diffusing film in one or two layers.
  • a light diffusing film may be arranged on the surface side of the lens sheet.
  • Patent Literature a film obtained by coating a light diffusing layer made of a transparent resin containing fine particles on the surface of a base film is used (Patent Literature). 1, 2).
  • the light diffusion film since it is necessary to provide a light diffusion layer by coating on one side of the base film, the light diffusion film has a bimetallic structure due to the difference in the linear expansion coefficient between the light diffusion layer and the base film. There is a problem that curling is likely to occur due to heating. This problem is becoming an important problem particularly in a liquid crystal display employing a direct type backlight unit that requires a large size and extremely high luminance such as a large liquid crystal TV. This is because the larger the area of the light diffusing film, the more the curling becomes more prominent, and the higher the brightness of the display, the greater the power consumption of the light source, that is, the amount of heat generated by the backlight unit. is there.
  • Patent Documents 3 4
  • the light diffusibility is imparted by the light scattering material inside the substrate, there is a problem that a part of the incident light causes back scattering and the light transmittance is lowered.
  • Patent Document 5 an approach has been made to impart light diffusibility to a biaxially stretched polyester film itself having excellent heat resistance, mechanical strength, and thickness uniformity.
  • characteristics that the biaxially stretched polyester film inherently have are impaired, or the light diffusive film should have a light diffusive film property such as light transmittance and light diffusibility. Is detrimental.
  • a light diffusing layer in which a melting point is 210 ° C. or less or amorphous polyester is used as a constituent resin, and a light diffusing additive composed of incompatible particles or thermoplastic resin is blended with the constituent resin is used as an intermediate layer.
  • a film in which a crystalline polyester resin layer is laminated on both sides is disclosed (see Patent Documents 6 to 13).
  • the biaxially stretched polyester film inherently has excellent heat resistance and mechanical strength by using a light diffusion layer mainly composed of crystalline polyester, and mainly imparts light diffusibility by surface haze.
  • a light diffusible polyester film having both total light transmittance and light diffusibility has been proposed (Patent Documents 14 and 15).
  • JP-A-6-59108 Japanese Patent No. 3698978 specification JP-A-9-281310 Japanese Patent No. 3732253 JP 2005-181648 A Japanese Patent Laid-Open No. 2001-324606 JP 2002-162508 A JP 2002-182013 A JP 2002-196113 A JP 2002-372606 A JP 2004-219438 A JP 2004-354558 A JP 2004-354558 A JP 2009-48156 A JP 2009-139684 A
  • the light diffusing polyester films disclosed in Patent Documents 14 and 15 have excellent mechanical strength, light diffusibility, and high light transmittance.
  • the light diffusing polyester film has a smooth surface opposite to the light diffusing layer surface, and it is possible to prepare a lens sheet by suitably providing a lens layer.
  • a lens layer is provided on a light-diffusing polyester film, a roll-type mold member that normally transfers the lens shape is used, and a light-diffusing polyester film in which a lens resin such as an ultraviolet curable resin is laminated is passed through while being active.
  • the lens layer is formed by applying energy.
  • an object of the present invention is to provide a light diffusible polyester film having excellent mechanical strength, light diffusibility, and high light transmittance, and excellent in high-temperature processability.
  • the present inventor solves the above problems by a light diffusible polyester film having a three-layer structure, each of which has a different action and structure, laminated by a coextrusion method. This has been found and the present invention has been achieved.
  • the light diffusable polyester film of the present invention capable of achieving the above object has the following constitution.
  • the first invention is a light diffusing polyester film made of a biaxially oriented polyester film, having a light diffusing layer (B) on one side of the intermediate layer (A), and on the opposite side. It consists of a three-layer structure laminated by a coextrusion method having a smooth layer (C), and the intermediate layer (A) is made of a crystalline homopolyester or a crystalline polyester containing a copolymer component, and the light diffusion layer (B) Comprises 50 to 99 parts by weight of a crystalline polyester containing a copolymer component having a melting point of 225 to 255 ° C. and 1 to 50 parts by weight of an additive incompatible with the polyester.
  • the smooth layer (C) has a melting point of A light diffusing polyester film comprising a crystalline polyester containing a copolymer component at 225 to 255 ° C.
  • the second invention is the light diffusing polyester film having a surface haze of 15% or more and an internal haze of less than the surface haze.
  • the third invention is the light diffusible polyester film, wherein the average slope gradient ( ⁇ a) of the surface of the light diffusion layer (B) is 0.03 or more.
  • the fourth invention is such that the dimensional change rate at 150 ° C.
  • the fifth invention has an average curl height of four corners of a rectangular film sample of 300 mm in the longitudinal direction and 210 mm in the width direction after heat treatment at 150 ° C. for 30 minutes in a heating oven. It is the said light diffusable polyester film which is 0 mm or less.
  • the sixth invention is the light diffusing polyester film having a total light transmittance of 86% or more and an image sharpness of 40% or less at a comb width of 2 mm.
  • the seventh invention is characterized in that at least one or more copolymer polyester resin, polyurethane resin, or acrylic resin provided on the surface of the light diffusion layer (B) before completion of stretching and orientation of the film is provided. It is the said light diffusable polyester film which has a coating layer which has as a main component.
  • the eighth invention provides at least a copolymer polyester resin, a polyurethane resin, or an acrylic resin on both surfaces of the light diffusing layer (B) and the smooth layer (C) of the light diffusing polyester film. It is the said light diffusable polyester film which has a coating layer which has 1 or more types as a main component.
  • the ninth invention is a coating comprising at least one copolymer polyester resin, polyurethane resin, or acrylic resin as a main component on the surface of the smooth layer (C) of the light diffusing polyester film. It is the light diffusable polyester film for lens sheets which has a layer.
  • the light diffusing polyester film of the present invention has excellent mechanical properties inherent to a biaxially stretched polyester film, and in addition to the effect of achieving both total light transmittance and light diffusibility, there is no curling due to heating, and is good High temperature workability.
  • the light diffusing polyester film of the present invention has a three-layer structure laminated by a coextrusion method having a light diffusing layer (B) on one side of the intermediate layer (A) and a smooth layer (C) on the opposite side.
  • the intermediate layer (A) is made of a crystalline homopolyester or a crystalline polyester containing a copolymer component
  • the light diffusion layer (B) is a crystalline polyester 50 containing a copolymer component having a melting point of 225 to 255 ° C.
  • the smooth layer (C) is made of a crystalline polyester containing a copolymer component having a melting point of 225 to 255 ° C., and 99 parts by weight and 1 to 50 parts by weight of an additive incompatible with the polyester. And The technical meaning of adopting such a special layer structure will be described in detail below.
  • the light diffusing polyester film of the present invention has a light diffusing layer (B) comprising a crystalline polyester containing a copolymer component and an additive incompatible with the polyester.
  • the crystalline polyester means a polyester having a melting point.
  • the melting point is the endothermic peak temperature at the time of melting detected at the time of primary temperature rise in so-called differential scanning calorimetry (DSC). If it is a polyester in which a clear crystal melting heat peak is observed as a melting point when measured using a differential scanning calorimeter, it is included in a crystalline polyester.
  • the polyester which comprises the light-diffusion layer (B) of this invention has a crystal structure, the mechanical characteristics peculiar to polyester films, such as heat resistance, mechanical strength, and thickness precision, are suitably hold
  • the crystal structure is large. Therefore, the higher the melting point of the polyester resin, the better.
  • the melting point of the polyester resin is high, the stretching stress generated during stretching increases, so if there is an incompatible additive in the resin, voids (cavities) are likely to occur, and the total light transmittance is reduced. To do. Therefore, in order to suppress the generation of voids while maintaining the mechanical properties as polyester, it is desirable to control the melting point of the resin constituting the light diffusion layer (B) within a certain range.
  • the lower limit of the melting point of the crystalline polyester containing the copolymer component constituting the light diffusion layer (B) is preferably 225 ° C, more preferably 230 ° C, and even more preferably 235 ° C. If melting
  • the melting point of the crystalline polyester constituting the light diffusion layer (B) can be controlled by introducing a copolymer component.
  • a copolymer component By introducing the copolymer component into the polyester, it is possible to suppress the generation of cavities and achieve both high light transmittance and light diffusibility. However, if the copolymer component is excessively introduced, the melting point of the polyester is lowered, and the original excellent characteristics of the biaxially stretched polyester film cannot be obtained.
  • the introduction amount of the copolymer component is preferably 3 mol% or more, more preferably 5 mol% or more, and particularly preferably 8 mol% or more with respect to the entire aromatic dicarboxylic component or the entire glycol component.
  • the content of the copolymer component is larger than 3 mol%, it is preferable because generation of voids is suppressed and the light transmittance and the light diffusibility are highly compatible.
  • the upper limit of the introduction amount of the copolymer component is preferably 20 mol% or less, more preferably 18 mol% or less, and particularly preferably 15 mol% or less with respect to the above components.
  • the melting point is such that the mechanical properties of the biaxially stretched polyester film are within the practical range.
  • the composition of the copolymer component that can be used in the present invention will be described later.
  • the light diffusing layer of the present invention contains an additive that is incompatible with polyester and exhibits suitable light diffusing properties.
  • the suitable aspect of the light-diffusion layer of this invention has the uneven
  • Light incident on the light diffusing layer (emitted from the light diffusing layer) is refracted and diffused in a random direction by the unevenness imparted to the film surface, and surface light diffusibility is exhibited. Therefore, it is desirable that the light diffusing film of the present invention has an internal haze less than the surface haze.
  • the diffusion of light in the light diffusion layer (B) is divided into scattering caused by the surface structure of the film and scattering caused by the internal structure of the film.
  • the scattering can be evaluated as surface haze, and the post-scattering can be evaluated as internal haze.
  • Light scattering by internal structures such as voids is accompanied by backscattering, so that a high total light transmittance cannot be obtained.
  • the light scattering by the surface structure can obtain high light diffusibility without greatly reducing the total light transmittance. Note that materials incompatible with the polyester that can be used in the present invention will be described later.
  • the light diffusing layer in the light diffusing polyester film of the present invention comprises a blended composition of 50 to 99 parts by mass of the crystalline polyester containing the copolymer component and 1 to 50 parts by mass of an additive incompatible with the polyester. .
  • a preferred blending ratio of both is a blend of 75 to 98 parts by weight of polyester and 2 to 25 parts by weight of additive, and more preferably a blend of 80 to 97 parts by weight of polyester and 3 to 20 parts by weight of additive.
  • the mixing ratio of the additive When the mixing ratio of the additive is less than 1 part by mass, the film surface unevenness forming ability by the additive is insufficient, and sufficient surface light diffusion performance cannot be obtained. On the other hand, when the mixing ratio of the additive exceeds 50 parts by mass, light scattering at the additive / polyester interface increases, and the stretching stress of the polyester increases to easily generate voids around the additive. As a result, the internal haze of the light diffusion layer increases, and the total light transmittance tends to decrease.
  • the surface haze of the light diffusion layer (B) tends to be higher as the surface irregularities are larger. Therefore, it is desirable that the particle size of the additive in the light diffusion layer (B) is large.
  • the lower limit of the thickness of the light diffusion layer (B) is preferably 3 ⁇ m or more, more preferably 4 ⁇ m, and particularly preferably 5 ⁇ m.
  • the thickness of the light diffusing layer (B) exceeds the particle size of the incompatible additive to a considerable extent, it becomes difficult to form a surface uneven structure effectively. Therefore, when the thickness of the light diffusion layer (B) is increased, the formation of surface irregularities is reduced and the surface haze is reduced. Further, according to the thickness of the light diffusion layer (B), the internal haze due to the internal structure of the light diffusion layer (B) increases, and the total light transmittance decreases. In order to achieve both high total light transmittance and light diffusibility, it is desirable to control the thickness of the light diffusion layer (B) within a predetermined range. Therefore, the upper limit of the thickness of the light diffusion layer (B) is preferably 50 ⁇ m, more preferably 30 ⁇ m, and particularly preferably 20 ⁇ m.
  • the tensile elastic modulus of the smooth layer (C) of the light diffusing polyester film of the present invention is preferably less than 4.0 MPa, more preferably 3.8 MPa or less, and even more preferably 3.7 MPa or less. preferable.
  • the tensile elastic modulus of the smooth layer (C) is not more than the above upper limit, flexibility suitable for lens processing is exhibited.
  • the tensile elastic modulus of the smooth layer (C) is preferably 2.0 MPa or more from the viewpoint of maintaining the mechanical strength of the film surface.
  • the light diffusing polyester film of the present invention preferably has a smooth layer (C) made of a crystalline polyester containing a copolymer component having a melting point of 225 to 255 ° C. From the viewpoint of the mechanical properties of the film as described above, the higher the melting point of the polyester resin, the better. However, in order to improve the flexibility of the film surface to which the lens layer is applied, it is desirable to control the melting point of the resin constituting the smooth layer (C) within a certain range.
  • 225 degreeC is preferable, as for the minimum of melting
  • the melting point of the crystalline polyester constituting the smooth layer (C) can be controlled by introducing a copolymer component.
  • the introduction amount of the copolymer component is preferably 3 mol% or more, more preferably 5 mol% or more, and particularly preferably 8 mol% or more with respect to the entire aromatic dicarboxylic component or the entire glycol component.
  • the upper limit of the introduction amount of the copolymer component is preferably 20 mol% or less, more preferably 18 mol% or less, and particularly preferably 15 mol% or less with respect to the above components.
  • the content of the copolymer component is 20 mol% or less, it is preferable because the melting point is such that the mechanical properties of the biaxially stretched polyester film are within the practical range.
  • the composition of the copolymer component that can be used in the present invention will be described later.
  • the surface of the smooth layer (C) is preferably a smooth surface so that processing such as lens processing and hard coat processing can be easily performed.
  • the three-dimensional surface roughness (SRa) of the smooth layer (C) is preferably 0.02 ⁇ m or less, and more preferably 0.01 ⁇ m or less.
  • the light-diffusing polyester film of the present invention has a three-layer structure as described above, and the two layers of the surface layer are each made of a crystalline polyester containing a copolymer component. Further, the light diffusing polyester film of the present invention has an intermediate layer (A) made of crystalline homopolyester or crystalline polyester containing a copolymer component.
  • the intermediate layer (A) mainly has an action of imparting mechanical strength of the film. That is, by providing the lower layer as a base film with the intermediate layer (A), the role of the smooth layer (C) can be shared, and both flexibility and lower back can be achieved.
  • the crystalline homopolyester / crystalline polyester constituting the intermediate layer (A) preferably has a high melting point from the viewpoint of mechanical properties.
  • the lower limit of the melting point is preferably 250 ° C. or higher, and more preferably 255 ° C. or higher.
  • the upper limit of the melting point is considered to be about 260 ° C. due to the properties of polyester.
  • each layer particularly the outermost layer, the light diffusion layer (B) and the smooth layer, are controlled by controlling the melting point and the layer thickness of the intermediate layer (A), the light diffusion layer (B), and the smooth layer (C).
  • the linear expansion coefficient and the elastic modulus in (C) are controlled to correspond to each other, curling can be suitably suppressed not only in the processing characteristics of the laminated body but also in the case where high temperature processing is performed.
  • the curl amount of the laminate having a bimetallic structure is determined by the heating temperature, the elastic modulus of each layer, and the linear expansion coefficient.
  • the above-mentioned physical property values act as a force that contracts or expands (thermal stress).
  • thermal stress is uneven in the thickness direction, the thermal stress is deformed from the planar shape and is a force that takes a stable structure by warping. work. Therefore, curling can be controlled by controlling the thermal stress in the thickness direction within an appropriate range. Therefore, the present inventors tried to optimize the thermal stress of each layer obtained by heating. That is, the laminated body was divided into two in the thickness direction, and the laminated structure was designed so that the upper half thermal stress and the lower half thermal stress were constant at an assumed temperature.
  • the thermal stress can be derived from the equations (1) and (2) based on linear elasticity theory in composite material mechanics.
  • ⁇ is the thermal stress
  • n is the number of divisions of the laminated film
  • l i is the distance between the center of the divided layer and the center line of the laminated film
  • ⁇ i is the thermal stress of the divided layer
  • E i is divided
  • T 1 is the temperature before heating
  • T 2 is the heating temperature
  • ⁇ i is the linear expansion coefficient when the temperature of the divided layer is changed from T 1 to T 2 .
  • the minimum unit of the three layers is 10 ⁇ m, so it is divided into 10 ⁇ m ⁇ 10 layers and multiplied by the thermal stress and the distance to the center line.
  • the moment difference between the upper half and the lower half can be obtained.
  • the difference in moment between the upper half and the lower half thus obtained is the thermal stress.
  • the thermal stress at 150 ° C.
  • thermal stress at 150 ° C. is within the above range, curling by heat treatment at 150 ° C. for 30 minutes can be suitably 3.0 mm or less.
  • the linear expansion coefficient and tensile elastic modulus between the light diffusion layer (B) and the smooth layer (C) which are the outermost layers should be adjusted to appropriate conditions.
  • the difference in linear expansion coefficient between the light diffusion layer (B) and the smooth layer (C) is preferably 1.2 ⁇ 10 ⁇ 5 / ° C. or less, and 1.0 ⁇ 10 ⁇ 5 / ° C. or less. More preferred is 0.5 ⁇ 10 ⁇ 5 / ° C. or less.
  • the difference in tensile elastic modulus between the light diffusion layer (B) and the smooth layer (C) is preferably 1.0 MPa or less, and more preferably 0.5 MPa or less.
  • the linear expansion coefficient and the tensile elastic modulus are correlated with the melting point as long as the polyester resin is used. Therefore, by controlling the melting point of each layer within the aforementioned range, curl control during heating can be suitably performed.
  • the smoothing layer (C) has a melting point corresponding to the melting point of the light diffusion layer (B). Desirably, it is made of a crystalline polyester containing a copolymer component at 225 to 255 ° C.
  • the lower limit of the melting point of the crystalline polyester containing the copolymer component constituting the smooth layer (C) is more preferably 230 ° C, further preferably 235 ° C, and further more preferably 240 ° C.
  • the upper limit of the melting point of the light diffusion layer is more preferably 250 ° C. In order to control the melting point of the crystalline polyester constituting the smooth layer (C), it can be controlled by the addition amount of the copolymerization component as described above.
  • the difference between the melting point of the light diffusion layer (B) and the melting point of the smooth layer (C) is preferably 10 ° C. or less, more preferably 8 ° C. or less, and further preferably 5 ° C. or less.
  • the melting point difference is 10 ° C. or less, the occurrence of curling during heating can be more suitably suppressed.
  • the ratio of the light diffusion layer (B) to the total film thickness is desirably controlled within a predetermined range, and preferably in the range of 2 to 50%.
  • the lower limit of the ratio of the light diffusion layer (B) to the total film thickness is preferably 2%, more preferably 3%, and particularly preferably 4%.
  • the upper limit of the ratio of the light diffusion layer (B) to the total film thickness is preferably 50%, more preferably 35%, and particularly preferably 20%.
  • the thickness of the smooth layer (C) is preferably controlled in correspondence with the light diffusion layer (B) in terms of controlling curling due to heating.
  • the thickness of the smooth layer (C) is preferably in the range of 5 to 50% of the total thickness, more preferably 10 to 40%, and further preferably 15 to 30%. Is preferred. When the thickness of the smooth layer (C) is within the above range, curling can be reduced more preferably.
  • the light diffusing polyester film of the present invention preferably has a curl of 3.0 mm or less by heat treatment at 150 ° C. for 30 minutes.
  • the curl is more preferably 2 mm or less, and further preferably 1.0 mm or less.
  • the curl measured under the above conditions is 3 mm or more, curl occurs in the film during post-processing at a high temperature, and therefore it may not be possible to maintain a high optical design when applying the lens layer.
  • the crystalline homopolyester used as a film raw material in the present invention includes aromatic dicarboxylic acids or esters thereof such as terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,4-butane. Polyester produced by polycondensation with glycols such as diol and neopentyl glycol.
  • these polyesters can be transesterified by an alkyl ester of an aromatic dicarboxylic acid and a glycol and then subjected to a polycondensation, or an aromatic method. It can be produced by a method such as polycondensation of diglycol ester of dicarboxylic acid.
  • polyesters include polyethylene terephthalate, polytrimethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate.
  • the polyester may be a homopolymer or may be a copolymer of the third component within a range that does not substantially impair the crystallinity thereof.
  • a polyester having an ethylene terephthalate unit or an ethylene-2,6-naphthalate unit of 70 mol% or more, preferably 80 mol% or more, more preferably 90 mol% or more is preferable.
  • the crystalline polyester containing a copolymerization component that can be used in the present invention is a polyester in which a third component (copolymerization component) is introduced into the main chain using the above crystalline homopolyester as a basic skeleton.
  • the structure, molecular weight, and composition are not limited and are arbitrary.
  • the light diffusing polyester film of the present invention comprises a copolymer polyester comprising an aromatic dicarboxylic acid component and a glycol component containing ethylene glycol and at least one branched aliphatic glycol or alicyclic glycol. It is preferable to use it for some or all of the raw materials.
  • Examples of branched aliphatic glycols include neopentyl glycol, 1,2-propanediol, and 1,2-butanediol.
  • Examples of the alicyclic glycol include 1,4-cyclohexanedimethanol and tricyclodecane dimethylol.
  • neopentyl glycol and 1,4-cyclohexanedimethanol are particularly preferable.
  • 1,3-propanediol or 1,4-butanediol is used as a copolymerization component in addition to the glycol component.
  • Introducing and using these glycols as copolymerization components in the above-mentioned range is suitable for imparting the above-mentioned characteristics, and further reduces voids in the light diffusion layer, and reduces light transmittance and light. It is also preferable from the viewpoint of achieving both high diffusibility.
  • one or more dicarboxylic acid components and / or glycol components as described below may be used in combination with the polyester as a copolymerization component.
  • dicarboxylic acid components that can be used in combination with terephthalic acid or its ester-forming derivatives include (1) isophthalic acid, 2,6-naphthalenedicarboxylic acid, diphenyl-4,4′-dicarboxylic acid, diphenoxyethanedicarboxylic acid Acid, diphenylsulfone dicarboxylic acid, 5-sodium sulfoisophthalic acid, aromatic dicarboxylic acid such as phthalic acid or ester-forming derivatives thereof, (2) oxalic acid, succinic acid, adipic acid, sebacic acid, dimer acid, maleic acid Aliphatic dicarboxylic acids such as fumaric acid and glutaric acid or ester-forming derivatives thereof, (3) alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid or ester-forming derivatives thereof, (4) p-oxybenzoic acid, Oxycarboxylic acids such as oxycaproic acid or
  • glycol components that can be used in combination with ethylene glycol and branched aliphatic glycol and / or alicyclic glycol include aliphatic glycols such as pentanediol and hexanediol, bisphenol A, bisphenol S, and the like. Aromatic glycols and their ethylene oxide adducts, diethylene glycol, triethylene glycol, dimer diol and the like can be mentioned.
  • the polyester may be further copolymerized with a polyfunctional compound such as trimellitic acid, trimesic acid, or trimethylolpropane.
  • a polyfunctional compound such as trimellitic acid, trimesic acid, or trimethylolpropane.
  • Examples of the catalyst used for producing the polyester include alkaline earth metal compounds, manganese compounds, cobalt compounds, aluminum compounds, antimony compounds, titanium compounds, titanium / silicon composite oxides, and germanium compounds. Of these, titanium compounds, antimony compounds, germanium compounds, and aluminum compounds are preferred from the viewpoint of catalytic activity.
  • a phosphorus compound as a heat stabilizer.
  • phosphorus compound phosphoric acid, phosphorous acid, etc. are preferable, for example.
  • the copolymer polyester may be used as a film raw material as it is, or a copolymer polyester having a large amount of copolymer components is blended with a homopolyester (for example, polyethylene terephthalate) to produce a copolymer. You may adjust the amount.
  • a homopolyester for example, polyethylene terephthalate
  • a co-polymer having a high melting point (heat resistance) while achieving both the light diffusibility and the total light transmittance equivalent to the case of using only the copolyester can be prepared.
  • a method may be employed in which two different kinds of crystalline polyesters are melt-mixed and a third component (copolymerization component) is introduced into the main chain by utilizing a transesterification reaction between them.
  • the copolymer polyester, polyethylene terephthalate, and at least one homopolyester other than polyethylene terephthalate are blended and used as a raw material for the light diffusing polyester film of the present invention.
  • the use is further preferable from the viewpoint of reducing voids.
  • the polyester constituting the intermediate layer (A) does not substantially contain particles.
  • the crystalline copolyester constituting the light diffusion layer (B) does not substantially contain particles other than the additive described later.
  • the above-mentioned “substantially contain no particles” means, for example, in the case of inorganic particles, a content of 50 ppm or less, preferably 10 ppm or less, particularly preferably a detection limit or less when inorganic elements are quantified by fluorescent X-ray analysis. Means quantity.
  • the lower limit of the intrinsic viscosity of the crystalline polyester is preferably 0.50 dl / g, more preferably 0.52 dl / g.
  • the intrinsic viscosity is less than 0.50 dl / g, when a foreign matter removing filter is provided in the melt line, the discharge stability during extrusion of the molten resin tends to be lowered.
  • crystalline polyester is used as the structure of the light diffusion layer (B)
  • the intrinsic viscosity of the crystalline polyester is increased, the shearing force during melting and stirring is increased.
  • An effective dispersion diameter may not be obtained to such an extent that a good uneven structure is imparted to the surface.
  • the upper limit of the intrinsic viscosity of the crystalline polyester is preferably 0.61 dl / g, more preferably 0.59 dl / g.
  • the intrinsic viscosity exceeds 0.61 dl / g, the dispersion diameter in the polyester of the additive becomes small, and the light diffusibility tends to decrease.
  • the additive in the present invention is added for the purpose of imparting unevenness to the surface of the light diffusion layer and exhibiting surface light diffusion performance.
  • the additive is not particularly limited as long as it is a material incompatible with polyester, and the following materials are preferably used.
  • thermoplastic resin incompatible with polyester The most excellent additive that can be used in the present invention is a thermoplastic resin that is incompatible with the polyester. That is, by utilizing the incompatibility between polyester and thermoplastic resin, in the production process (melting / extrusion process) of the biaxially stretched film, the matrix made of polyester is made of a thermoplastic resin that is incompatible with the polyester. This is a technology that forms domains in a dispersed manner and uses them as surface irregularity forming agents. Since incompatible thermoplastic resins are easily deformed by heating, they are suitable for suppressing the generation of voids inside the film and forming a concavo-convex shape suitable for light diffusibility. In addition, by using this technique, foreign matter is filtered with a high-accuracy filter in the film melting / extrusion step, and the cleanliness necessary for a liquid crystal display film can be achieved.
  • polyolefins such as polyethylene, polypropylene, polymethylpentene, various cyclic olefin polymers, polycarbonate, polystyrene such as atactic polystyrene, syndiotactic polystyrene, iso
  • an amorphous transparent polymer in order to produce a film having a high light transmittance.
  • a crystalline polymer when used as an additive, the crystalline polymer becomes cloudy, the internal haze of the film increases, and the light transmittance may decrease.
  • amorphous transparent polymer examples include the following. That is, polystyrene (PS resin), acrylonitrile / styrene copolymer (AS resin), methyl methacrylate / styrene copolymer (MS resin), cyclic olefin polymer, methacrylic resin, PMMA, and the like are exemplified.
  • an amorphous transparent polymer having a polymer surface tension close to that of a matrix made of polyester it is more preferable from the viewpoint of void reduction to select an amorphous transparent polymer having a polymer surface tension close to that of a matrix made of polyester.
  • an amorphous transparent polymer having a surface tension close to that of polyester polystyrene (PS resin), PMMA and the like are particularly preferable.
  • the difference in melt viscosity between the crystalline polyester containing the copolymerization component constituting the light diffusion layer (B) and the incompatible thermoplastic resin is large.
  • the difference in melt viscosity is preferably 35 Pa ⁇ s or more, and more preferably 40 Pa ⁇ s or more.
  • Non-melting polymer particles The non-melting polymer particles that can be used as the additive of the present invention are obtained when the temperature is raised from 30 ° C. to 350 ° C. at 10 ° C./min using a melting point measuring device (manufactured by Stanford Research Systems, MPA100 type).
  • the composition of the particles is not limited as long as the particles do not undergo flow deformation due to melting. Examples thereof include acrylic resins, polystyrene resins, polyolefin resins, polyester resins, polyamide resins, polyimide resins, fluorine resins, urea resins, melamine resins, and organic silicone resins.
  • the shape of the particles is preferably spherical or elliptical. The particles may or may not have pores. Furthermore, you may use both together.
  • non-melting polymer particles are made of a polymer having a melting point of 350 ° C. or higher, non-cross-linked polymer particles may be used, but from the viewpoint of heat resistance, cross-linked polymer particles made of a polymer having a cross-linked structure are used. It is preferable.
  • the average particle size of the non-melting polymer particles is preferably 0.1 to 50 ⁇ m.
  • the lower limit of the average particle size of the non-melting polymer particles is more preferably 0.5 ⁇ m, and particularly preferably 5 ⁇ m.
  • the average particle size of the non-melting polymer particles is preferably 0.1 ⁇ m or more.
  • the upper limit of the average particle diameter of the non-melting polymer particles is more preferably 30 ⁇ m, and particularly preferably 20 ⁇ m.
  • the non-melting polymer particles are preferably particles having a sharp particle size distribution as much as possible.
  • the above non-melting polymer particles may be one kind or two or more kinds.
  • grain is performed with the following method. Take a photograph of the particles with a scanning electron microscope (SEM), measure the maximum diameter of 300-500 particles at a magnification such that the size of one smallest particle is 2-5 mm, and calculate the average value. Average particle diameter. Moreover, when the particle
  • SEM scanning electron microscope
  • inorganic particles examples include silica, calcium carbonate, barium sulfate, calcium sulfate, alumina, kaolinite, talc and the like.
  • the average particle size of the inorganic particles is usually preferably 0.1 to 50 ⁇ m. 0.5-30 ⁇ m is more preferable, and 1-20 ⁇ m is even more preferable. If the average particle size is less than 0.1 ⁇ m, a good light diffusion effect cannot be obtained. On the contrary, when it exceeds 50 ⁇ m, it is not preferable because it leads to a decrease in film strength and the like. It is preferable that the particle size distribution of the inorganic particles is as sharp as possible. When it is necessary to widen the particle size distribution, it is preferable to mix a plurality of particles having a sharp particle size distribution. By the correspondence, mixing of particles having a large particle diameter, which is a defect of the film, can be suppressed.
  • grain is performed with the following method. Take a photograph of the particles with a scanning electron microscope (SEM), measure the maximum diameter of 300-500 particles at a magnification such that the size of one smallest particle is 2-5 mm, and calculate the average value. Average particle diameter. Moreover, the maximum diameter of the particle
  • SEM scanning electron microscope
  • the shape of the above inorganic particles is not limited, but is preferably substantially spherical or true spherical.
  • the particles may be non-porous or porous. Furthermore, you may use both together.
  • the additive used in the present invention may be one of the above three types, or two or more types may be used in combination.
  • the light diffusing polyester film of the present invention preferably has a plane orientation coefficient ( ⁇ P) of 0.08 to 0.16.
  • the lower limit of the plane orientation coefficient ( ⁇ P) is more preferably 0.09, and particularly preferably 0.10.
  • the upper limit of the plane orientation coefficient ( ⁇ P) is more preferably 0.15, and particularly preferably 0.14.
  • the plane orientation coefficient is 0.08 or more, the characteristics as a biaxially stretched film are exhibited, heat resistance, mechanical strength, thickness uniformity and the like are good, and the occurrence of heating curl is suppressed.
  • the method for controlling the plane orientation coefficient within the above range is arbitrary, but can be controlled, for example, by adjusting the ratio of the copolymer component to the crystalline polyester containing the copolymer component. If the ratio of the copolymer component in the light diffusing layer or the smooth layer is increased, the plane orientation coefficient is decreased, and if the ratio of the copolymer component is decreased, the plane orientation coefficient can be increased.
  • the ratio of the preferable copolymerization component is as described above.
  • the surface haze is preferably 5% or more, more preferably 10% or more, further preferably 15% or more, and the internal haze is preferably less than the surface haze.
  • the surface haze is a characteristic derived from surface irregularities of the light diffusion layer. Therefore, when light is emitted from the film surface, or when light is incident on the film surface, the surface haze is increased due to the light being refracted by the surface irregularities of the light diffusion layer. Therefore, surface haze and total light transmittance are basically irrelevant. Therefore, by increasing the surface haze, the light diffusibility can be enhanced in a state where the decrease in the total light transmittance is suppressed.
  • the internal haze is a characteristic derived from light scattering inside the film. Therefore, the total light transmittance is reduced due to the influence of backscattering of incident light. Therefore, in order to produce a light diffusible polyester film having excellent light diffusibility and high total light transmittance, it is effective means to increase the surface haze and reduce the internal haze as much as possible.
  • an incompatible thermoplastic resin as the light diffusing additive. The incompatible thermoplastic resin is easily deformed by heating, and generation of voids inside the film that causes internal haze can be suitably suppressed.
  • the surface haze of the light diffusing polyester film of the present invention is preferably 5% or more, more preferably 10% or more, further preferably 15% or more, and a still more preferable lower limit is 20%.
  • a still more preferable lower limit is 20%.
  • the preferable upper limit of the surface haze is 60%, the more preferable upper limit is 70%, and the more preferable upper limit is 80%. If the surface haze is 80% or less, the internal haze may be suppressed and the total light transmittance may be increased.
  • the internal haze is preferably less than the surface haze.
  • the upper limit of the internal haze is preferably 40%, more preferably 30%, still more preferably 20%, and particularly preferably 10%.
  • the internal haze is responsible for the light diffusing function of the film, causing light scattering (with backscattering) inside the film and total light transmission. The rate is greatly reduced.
  • the lower limit of the internal haze is preferably 1%. In a film having an internal haze of less than 1%, sufficient surface haze tends not to be obtained.
  • the light diffusing polyester film of the present invention desirably has a total light transmittance of 86% or more.
  • a more preferable lower limit of light transmittance is 87%, and a more preferable lower limit is 88%.
  • the light diffusion performance of the light diffusing film can be quantitatively evaluated by, for example, the image definition.
  • Image sharpness is an index indicating the sharpness when a light source such as a fluorescent lamp is viewed through a film, and is a normal method for measuring in accordance with JIS K 7105 “Plastic Optical Properties Test Method” image sharpness. This is the image definition evaluated in. The smaller the image definition, the better the concealing property and the better the light diffusion performance.
  • the light diffusing polyester film of the present invention it is possible to obtain an image definition of 50% or less in the transmission method with an optical comb width of 2 mm.
  • a more preferable upper limit of image definition is 40%, and a further preferable upper limit is 20%. Note that the smaller the image definition, the better. However, if the image definition is to be reduced more than necessary, the internal haze increases and the total light transmittance decreases.
  • the lower limit of the image definition is preferably 1%, more preferably 3%.
  • the light emitted from the light emitter passes through the light diffusing film and the lens sheet.
  • the light rays diffused by the light diffusing film are emitted in the front direction after the focusing angle is adjusted mainly in the prism type lens provided on the lens sheet.
  • the light diffusing film has an optical design that can provide not only diffusibility but also a predetermined front luminance when combined with a lens sheet.
  • the ratio of the amount of light that is captured and collected by the lens sheet, prism sheet, and lens layer is reduced, so that the brightness of transmitted light emitted to the front surface is lowered.
  • the ratio of the amount of light captured and condensed by the lens sheet or the lens layer is increased, but the diffused component is reduced. For this reason, the light diffusibility of the transmitted light is lowered, and the concealability by the diffusion film and the uniformity of the luminance over the entire irradiated surface are lowered. Therefore, it is preferable to achieve a high degree of compatibility between the luminance when the lens sheet or the lens layer is combined and the diffusibility of the light diffusion film alone.
  • the inventors of the present invention diligently studied how to obtain a film having an optimal optical design in accordance with the condensing angle of the lens sheet. As a result, the present inventor controlled light diffusion by controlling the average gradient ( ⁇ a) of the surface of the light diffusion layer. As a result, a light diffusive film having an optical design that exhibits excellent frontal brightness when combined with a lens sheet is realized.
  • the average gradient ( ⁇ a) is obtained from the surface unevenness profile observed on the micromap.
  • the height (y) of the surface unevenness profile was measured at every predetermined pitch (x), and the difference in height (y n ⁇ y n + 1 ) at two consecutive measurement points was divided by the measurement pitch interval (x).
  • the product was defined as a slope, and the longitudinal direction (the longitudinal direction of the film) was measured over a predetermined length in two directions orthogonal to the transverse direction (the width direction of the film), and the average was obtained as the average slope gradient ( ⁇ a).
  • the average gradient ( ⁇ a) expresses an average gradient (gradient) due to the uneven structure formed on the surface of the light diffusion layer.
  • the average inclination gradient ( ⁇ a) is a factor that governs the coexistence of the light diffusion caused by the uneven structure on the surface of the light diffusion layer and the luminance exhibited when combined with the lens sheet.
  • the average slope gradient ( ⁇ a) on the surface of the light diffusion layer is preferably 0.03 or more.
  • ⁇ a is 0.03 or more, not only the light diffusibility necessary for concealing properties such as a cathode ray tube, but also sufficient brightness when combined with the lens film even at a low irradiation amount. it can.
  • the lower limit of ⁇ a is preferably 0.04 or more, and more preferably 0.05 or more.
  • the upper limit of ⁇ a is preferably 0.10 or less, more preferably 0.09 or less, and even more preferably 0.08 or less. If ⁇ a exceeds 0.10, depending on the lens sheet used, back reflection due to in-plane reflection may occur due to optical design, and the front luminance may not be improved.
  • composition having an incompatible additive constituting the light diffusion layer (B) contributes to effective formation of unevenness in the stretching process. This is considered to be due to the incompatible additive being pushed out by the stretching stress generated inside the film in the stretching process to form an effective uneven structure.
  • the concavo-convex structure is flattened in the subsequent film forming process, and the concavo-convex having an average inclination gradient ( ⁇ a) that produces a predetermined luminance when combined with the lens sheet.
  • ⁇ a average inclination gradient
  • the structure is not retained.
  • a heat treatment at a high temperature of 235 to 250 ° C. may be performed in the heat treatment step.
  • the crystalline polyester containing the copolymer component constituting the light diffusing layer (B) may be softened by high-temperature heat treatment, and the gradient of the concavo-convex structure formed in the stretching process may be flattened.
  • the average gradient ( ⁇ a) of the present invention it is desirable to increase the difference between the melting point of the resin constituting the light diffusion layer (B) and the heat treatment temperature.
  • the difference between the melting point of the resin constituting the light diffusion layer (B) and the heat treatment temperature is reduced, the light diffusion layer is softened in the heat treatment step, and as a result, surface irregularities having an average gradient ( ⁇ a) excellent in luminance. No structure is formed.
  • the difference between the melting point of the resin constituting the light diffusion layer (B) and the heat treatment temperature is increased, the heat treatment temperature is lowered, so that the thermal contraction rate of the film is deteriorated.
  • the difference between the melting point of the light diffusion layer (B) and the heat treatment temperature is preferably controlled within a range of 9 ° C. or more and 25 ° C. or less, more preferably 11 ° C. or more and 23 ° C. or less, More preferably, it is 13 ° C. or more and 21 ° C. or less.
  • the dimensional change rate at 150 ° C. is preferably 3% or less in both the horizontal direction and the vertical direction, the more preferable upper limit is 2.5%, and the more preferable upper limit is 2%.
  • a preferred upper limit is 1.5%, and a more particularly preferred upper limit is 1%.
  • a smaller dimensional change rate in the horizontal and vertical directions at 150 ° C. is desirable, but 0% is considered the lower limit.
  • the longitudinal direction refers to the film flow direction (winding direction) during film formation
  • the lateral direction refers to a direction perpendicular thereto.
  • the lower limit of the tensile strength of the film is preferably 100 MPa, more preferably 130 MPa, and particularly preferably 160 MPa.
  • the tensile strength is 100 MPa or more, the mechanical strength of the biaxially stretched film is exhibited, and problems such as cracks, tears, breaks, and tears are less likely to occur in the film processing step.
  • the lower limit of the tensile elongation of the film is preferably 100%, more preferably 120%, and particularly preferably 140%.
  • the tensile elongation is 100% or more, flexibility is imparted to the film, and problems such as cracking, tearing, breaking, and tearing are less likely to occur in the winding and cutting process even after lens coating.
  • the light diffusing polyester film of the present invention preferably has a thickness unevenness of 5.0% or less.
  • the thickness unevenness of the film is 5.0% or less, when the film is wound on a roll, it is difficult to cause wrinkles and bumps, and flatness is maintained. As a result, the luminance of the light exit surface of the backlight unit becomes uniform, and the original purpose of the light diffusing film can be achieved.
  • the thickness of the light diffusing polyester film of the present invention is arbitrary and is not particularly limited, but is preferably in the range of 25 to 500 ⁇ m, more preferably in the range of 75 to 350 ⁇ m.
  • the mechanical properties and optical properties of the film can also be controlled by the film forming conditions.
  • the stretching temperature of the film When the stretching temperature of the film is raised, the stretching stress is lowered, so the orientation coefficient is lowered and the generation of voids is suppressed. Further, since surface irregularities due to incompatible additives are easily formed, it is desirable to stretch at a high temperature from the viewpoint of achieving both the total light ray transmittance and the light diffusibility. However, when the stretching temperature is increased, the thickness variation of the film increases, resulting in thickness unevenness and the like, and it is difficult to obtain the original mechanical characteristics of the film.
  • the temperature during stretching is preferably in the temperature range of 120 ° C to 160 ° C.
  • polyester a polyethylene terephthalate copolymer
  • B a crystalline polyester containing a copolymer component that is a raw material of the light diffusion layer (B).
  • polyester and a thermoplastic resin incompatible with the polyester are dried by vacuum drying or hot air drying so that the moisture content is less than 100 ppm.
  • each raw material is weighed and mixed, supplied to an extruder, and melt extruded into a sheet. Further, the molten sheet is brought into close contact with a metal rotating roll (chill roll) controlled at a surface temperature of 10 to 50 ° C. using an electrostatic application method to obtain an unstretched PET sheet.
  • the incompatible additive is used as a pre-kneading master pellet in which all or part of the base polymer and the incompatible additive are previously melt-mixed using an extruder. is important.
  • the resin temperature up to the melting section, kneading section, polymer tube, gear pump, and filter of the extruder is controlled to 220 to 290 ° C.
  • the resin temperature up to the subsequent polymer tube and die is controlled to 210 to 295 ° C.
  • high-precision filtration is performed at any place where the molten resin is maintained at a constant temperature of 275 ° C. in order to remove foreign substances contained in the resin.
  • the filter medium of stainless steel sintered body is capable of removing aggregates mainly composed of Si, Ti, Sb, Ge, Cu and high melting point organic substances in the resin. Excellent and suitable.
  • the filter particle size (initial filtration efficiency 95%) of the filter medium is preferably 20 ⁇ m or less, particularly preferably 15 ⁇ m or less.
  • the filter particle size (initial filtration efficiency 95%) of the filter medium exceeds 20 ⁇ m, it becomes difficult to sufficiently remove foreign matters having a size of 20 ⁇ m or more.
  • Productivity may be reduced by performing high-precision filtration of molten resin using a filter medium having a filter particle size (initial filtration efficiency of 95%) of 20 ⁇ m or less.
  • a film with less optical defects due to coarse particles may be used. It is an important process to obtain.
  • high-accuracy filtration as described above can be performed by using an incompatible thermoplastic resin for the crystalline copolyester as an additive.
  • the raw materials of each layer are extruded using two or more extruders, and a multi-layer feed block (for example, square
  • the layers are joined using a joining block having a joining part), extruded from a slit-like die into a sheet, and cooled and solidified on a casting roll to produce an unstretched film.
  • a multi-manifold die may be used instead of the multilayer feed block.
  • the light diffusable polyester film of this invention it is preferable to have a coating layer on at least one surface, and also it is preferable to have a coating layer on both surfaces.
  • a preferable coating amount is in the range of 0.005 to 0.20 g / m 2 .
  • biaxial stretching is performed after an application layer is provided on the unstretched film obtained by the above method.
  • the simultaneous biaxial stretching method or the sequential biaxial stretching method may be used.
  • an easy-adhesion layer is provided on a film uniaxially stretched in the longitudinal or transverse direction, and then stretched in the orthogonal direction and biaxially stretched. I do.
  • the method for applying the coating layer forming coating solution to an unstretched film or a uniaxially stretched film can be selected from known arbitrary methods, such as reverse roll coating, gravure coating, kiss coating, and die coater. Method, roll brush method, spray coating method, air knife coating method, wire bar coating method, pipe doctor method, impregnation coating method, curtain coating method, and the like. These methods are applied alone or in combination.
  • the resin constituting the coating layer is a copolyester resin, polyurethane resin, or acrylic resin from the viewpoint of ensuring better adhesion to other optical functional layers in lens sheet applications and light diffusing film applications. It is preferable that at least one of these is a main component. These resins are also recommended from the viewpoint of suppressing the generation of reflected light on the surface of the light diffusion layer.
  • the “main component” means that at least one of the resins is contained in an amount of 50% by mass or more with respect to 100% by mass of the resin constituting the coating layer. Means.
  • the particles are not contained in the intermediate layer (A) or are contained in such a small amount that the transparency is not hindered, the slipperiness of the film becomes insufficient and handling properties are improved. It may get worse. Therefore, it is preferable to contain particles in the coating layer for the purpose of imparting slipperiness. For these particles, it is important to use particles having an extremely small average particle diameter equal to or smaller than the wavelength of visible light in order to ensure transparency.
  • the particles include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, and molybdenum sulfide; crosslinked polymer particles; calcium oxalate And organic particles.
  • Silica is particularly preferable when the coating layer is formed mainly of the copolymer polyester resin. Since silica has a relatively close refractive index to that of polyester, it is most preferable in that a light diffusible polyester film having more excellent transparency can be secured.
  • the particles contained in the coating layer have an average particle diameter (average maximum diameter of number-based particles observed by SEM) of 0.005 to 1.0 ⁇ m, so that the transparency, handling properties, and scratch resistance of the film It is preferable from the viewpoint of securing.
  • the upper limit of the average particle size of the particles is more preferably 0.5 ⁇ m, particularly preferably 0.2 ⁇ m, from the viewpoint of transparency.
  • the lower limit of the average particle diameter of the particles is more preferably 0.01 ⁇ m, particularly preferably 0.03 ⁇ m from the viewpoints of handling properties and scratch resistance.
  • grain is performed with the following method. Take a photograph of the particles with a scanning electron microscope (SEM), measure the maximum diameter of 300-500 particles at a magnification such that the size of one smallest particle is 2-5 mm, and calculate the average value. Average particle diameter.
  • SEM scanning electron microscope
  • the cross section of the coating film is measured using a transmission electron microscope (TEM) at a magnification such that the size of one smallest particle is 2 to 5 mm.
  • TEM transmission electron microscope
  • the maximum diameter of particles existing in the cross section of the coating layer is obtained.
  • the average particle size of the aggregated particles is measured by taking 300 to 500 cross sections of the coated layer of the coated film using an optical microscope at a magnification of 200 times and measuring the maximum diameter.
  • the content of the particles in the coating layer is 0.1 to 60% by mass with respect to the composition constituting the coating layer.
  • the transparency, adhesion, handling properties, and scratch resistance of the laminated optical film are as follows. It is preferable from the viewpoint of ensuring.
  • the upper limit of the content of particles is more preferably 50% by mass, particularly preferably 40% by mass, from the viewpoints of transparency and adhesion.
  • the lower limit of the content of the particles is more preferably 1% by mass, particularly preferably 0.5% by mass from the viewpoints of handling properties and scratch resistance.
  • Two or more kinds of the particles may be used in combination, and the same kind of particles having different particle sizes may be blended, but in any case, the average particle size of the whole particles and the total content are within the above range. Is preferably satisfied.
  • the unstretched film obtained by the above method is simultaneously biaxially stretched or sequentially biaxially stretched, and then heat-treated.
  • the draw ratio defined by this invention is the actual draw ratio by which the film was actually extended
  • the draw ratio in either the machine direction or the transverse direction is less than 2.8 times, the thickness unevenness of the resulting film is lowered, and the original excellent heat resistance and mechanical strength of the biaxially stretched film cannot be obtained. . In addition, the film thickness uniformity is significantly deteriorated.
  • the lower limit of the preferred draw ratio in the present invention is 3.0 times, and the more preferred lower limit is 3.2 times. Moreover, the preferable upper limit of a draw ratio is 5 times.
  • the temperature during the transverse stretching is preferably within a temperature range of 120 ° C to 160 ° C.
  • the heat treatment is preferably performed within a temperature setting range of 220 to 250 ° C. and a range of 5 seconds to 100 seconds under a condition where the air volume is 25 m / min or more.
  • the stretching temperature of the film When the stretching temperature of the film is increased, the stretching stress is lowered, so that the orientation coefficient is lowered and the generation of voids is suppressed. Further, since surface irregularities due to incompatible additives are easily formed, it is desirable to stretch at a high temperature from the viewpoint of achieving both the total light ray transmittance and the light diffusibility. Further, when the heat treatment is performed at a high temperature, voids disappear and the internal haze can be lowered. However, when the stretching temperature is increased, the thickness variation of the film increases, resulting in thickness spots and the like, and it may be difficult to obtain the original mechanical characteristics of the film.
  • Thickness unevenness is 5% or less
  • the same operation was performed 150 times continuously at intervals of 2 ⁇ m in the width direction of the film, that is, over 0.3 mm in the width direction of the film, and the data was taken into the analyzer.
  • the center plane average roughness (SRa) was determined using an analyzer.
  • the haze (cloudiness value) and total light transmittance of the film test piece were measured in accordance with JIS K 7105 "Testing methods for optical properties of plastics".
  • the film test piece was placed with the longitudinal direction of the film in the vertical direction and the light diffusion layer (B) faced toward the light source, and measured using a NDH-300A type turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd.
  • the haze of the internal haze measurement sample and the blank sample was measured by the method described in (6). Then, the haze value of the blank sample was subtracted from the haze value of the sample for measuring internal haze to determine the internal haze. Further, the haze of the film test piece alone measured by the method described in (6) was defined as the total haze, and the internal haze value was subtracted from the total haze value to determine the surface haze.
  • Image Sharpness Measured by the transmission method in accordance with JIS K 7105 “Testing method for optical properties of plastic” image sharpness The film test piece was measured with the film longitudinal direction as the vertical direction and the surface of the light diffusion layer (B) facing the light source.
  • a measuring instrument an ICM-1T image clarity measuring instrument manufactured by Suga Test Instruments Co., Ltd. was used.
  • Tensile modulus A film sample of each layer alone was collected. The tensile elastic modulus of each layer was measured according to JIS K 7161 using a Toyo Baldwin strong elongation analyzer (TMI RTM-100).
  • Curling value Curling during high temperature heating is measured by the following methods (a) to (f).
  • a rectangular film sample having a length of 300 mm in the film formation and 210 mm in the width direction is cut out.
  • B) The sample is placed on a flat mount with the light diffusion layer (B) side up, and is placed on a shelf plate of a heating oven adjusted to 150 ° C., and heat-treated for 30 minutes.
  • the room temperature condition is desirably a condition controlled at a temperature of 23 ⁇ 2 ° C. and a humidity of 65 ⁇ 5%.
  • ⁇ a [(y 1 ⁇ 0) /2.5+ (y 2 ⁇ y 1 ) /2.5+ ⁇ + (y n ⁇ y n ⁇ 1 ) /2.5] / n
  • Luminance ratio As a lens sheet to be combined with the luminance evaluation of the obtained surface light diffusion film, a lens sheet mounted on a liquid crystal television manufactured by Sharp Corporation (Aquos LC-37GS10, manufactured in 2007) was used. Two films were overlapped so as to overlap the intermediate layer (A) surface of the cut light diffusing film piece and the lens back surface of the lens sheet. The light diffusive film piece was placed on the turbidimeter with the light diffusion layer (B) surface facing the light source so that the vertical direction of the light diffusive film piece (longitudinal direction of film formation) was the vertical direction. The NDH-300A type turbidimeter manufactured by Nippon Denshoku Industries Co., Ltd. was used as the turbidimeter.
  • the measurement method was carried out in accordance with JIS K 7105 “Testing method for optical properties of plastics”. Deriving a value obtained by dividing the parallel light transmittance obtained by measurement by the total light transmittance, and a luminance ratio (%) to a value obtained by dividing the parallel light transmittance obtained by measuring the lens sheet alone by the total light transmittance ) was derived.
  • Example 1 Production of crystalline homopolyester resin (M1) When the temperature of the esterification reaction can reached 200 ° C, from terephthalic acid (86.4 parts by mass) and ethylene glycol (64.4 parts by mass) The resulting slurry was added and antimony trioxide (0.017 parts by mass) and triethylamine (0.16 parts by mass) were added as catalysts while stirring. Next, the pressure was increased and the pressure esterification reaction was performed under the conditions of a gauge pressure of 3.5 kgf / cm 2 and 240 ° C. Thereafter, the inside of the esterification reaction vessel was returned to normal pressure, and magnesium acetate tetrahydrate (0.071 parts by mass) and then phosphoric acid (0.014 parts by mass) were added.
  • M1 Production of crystalline homopolyester resin (M1) When the temperature of the esterification reaction can reached 200 ° C, from terephthalic acid (86.4 parts by mass) and ethylene glycol (64.4 parts by mass) The resulting slurry was added and antimony
  • esterification reaction product was transferred to a polycondensation reaction can, gradually heated from 260 ° C. to 280 ° C. under reduced pressure, and subjected to a polycondensation reaction at 285 ° C. until a predetermined intrinsic viscosity was reached. went.
  • the obtained crystalline homopolyester resin (M1) had a heat of crystal fusion of 35 mJ / mg, a melting point of 256 ° C., an intrinsic viscosity of 0.56 dl / g, and a melt viscosity of 91 Pa ⁇ s. Further, inert particles and internally precipitated particles were not substantially contained.
  • Polystyrene (M3) A polystyrene resin (PS) having a melt viscosity of 147 Pa ⁇ s was used.
  • Extruder 2 Extruder 3, and Extruder are set to a melt temperature, a kneading section, a polymer tube, a gear pump, a filter at a set temperature of 275 ° C., and a polymer tube after the filter at a set temperature of 270 ° C.
  • Each raw material supplied from 1 was laminated using a three-layer merging block, and melt-extruded into a sheet form from a die.
  • the thickness ratio of the (B) layer, (A) layer, and (C) layer was controlled using the gear pump of each layer so that it might become 11: 78: 1.
  • a stainless sintered body filter material (nominal filtration accuracy: 95% cut of 10 ⁇ m particles) was used for each of the filters. The temperature of the die was controlled so that the temperature of the extruded resin was 275 ° C.
  • the extruded resin was brought into close contact with a cooling drum having a surface temperature of 30 ° C. using an electrostatic application method and cooled and solidified to prepare an unstretched film.
  • the (C) layer surface was a surface in contact with the cooling drum.
  • the take-up speed of the unstretched film by the cooling drum was 12 m / min.
  • the obtained unstretched film was heated to 79 ° C. using a preheating roll, and stretched 3.4 times in the flow direction between rolls having different peripheral speeds. At this time, the temperature of the film was monitored with an infrared radiation thermometer, and the heater temperature was controlled so that the maximum temperature of the film was 100 ° C.
  • the obtained uniaxially stretched film was cooled to 50 ° C., and then the coating liquid (M4) was applied to both surfaces of the film.
  • the amount of solution applied was controlled so that the final film thickness was 0.08 g / m 2 on both sides. Thereafter, the coated surface was dried in a drying furnace.
  • the both ends of the uniaxially stretched film having the coating layer are gripped with clips, guided to a tenter, preheated to 120 ° C, stretched 2.5 times in the width direction at 135 ° C, and then 1.6 times in the width direction at 140 ° C.
  • the film was stretched twice, further heat treated at 231 ° C. for 10 seconds, and subjected to a relaxation treatment of 3.3% in the width direction in the process of cooling to 60 ° C., thereby producing a light-diffusing polyester film having a total thickness of 188 ⁇ m.
  • the properties of the film obtained in Example 1 are shown in Table 1.
  • the light diffusing polyester film obtained in the present invention has the heat resistance, mechanical strength, and thickness accuracy inherent to the biaxially stretched film.
  • the internal haze is small and the light transmittance is high.
  • it can be seen that most of the total haze is imparted by the surface haze, and the light diffusibility is also excellent. In addition, curling is hardly observed even during high temperature treatment.
  • Example 2 As raw materials for the smooth layer (C), 87 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) 13 dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. The mass part was mixed and supplied to the extruder 3, the thickness ratio of the (B) layer, the (A) layer, and the (C) layer was controlled to be 11:67:22, in the width direction. After stretching, a light diffusing polyester film of Example 2 was prepared in the same manner as shown in Example 1 except that the film was heat treated at 222 ° C. for 10 seconds.
  • M1 crystalline homopolyester
  • M2 copolymer polyester
  • Example 2 The characteristics of the film obtained in Example 2 are shown in Table 1. From Table 1, it can be seen that Example 2 has excellent characteristics as in Example 1.
  • Example 3 As raw materials for the light diffusion layer (B), 51 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. 46 parts by mass and 3 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2.
  • a raw material for the smooth layer (C) a crystalline homopolyester (1 Torr) dried at 135 ° C. under reduced pressure for 6 hours (1 Torr) M1) 53 parts by mass and 47 parts by mass of copolyester (M2) dried at 70 ° C.
  • Example 3 having a thickness of 100 ⁇ m was performed in the same manner as shown in Example 1 except that 1.0% relaxation treatment was performed in the width direction in the process of heat treatment for 2 seconds and cooling to 60 ° C.
  • a conductive polyester film was prepared.
  • Example 3 The characteristics of the film obtained in Example 3 are shown in Table 1. From Table 1, it can be seen that the present Example 3 has excellent characteristics as in Example 1.
  • Example 4 As raw materials of the light diffusion layer (B), 69 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. 21 parts by mass and 10 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2.
  • a raw material for the smooth layer (C) As a raw material for the smooth layer (C), a crystalline homopolyester (1 Torr) dried at 135 ° C. for 6 hours under reduced pressure (1 Torr) M1) 67 parts by mass and 33 parts by mass of copolyester (M2) dried under reduced pressure (1 Torr) at 70 ° C.
  • Example 4 Te For 12 hours were supplied to the extruder 3, heat treated at 232 ° C. for 17 seconds, thickness The same method as shown in Example 3 except that the thickness was adjusted to 100 ⁇ m and the thickness ratio of the (B) layer, the (A) layer, and the (C) layer was 11: 84: 7. It created a light-diffusing polyester film of Example 4 Te.
  • Example 4 The properties of the film obtained in Example 4 are shown in Table 1. From Table 1, it can be seen that Example 4 has excellent characteristics as in Example 1.
  • Example 5 As raw materials for the light diffusion layer (B), 55 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. 38 parts by mass and 7 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2.
  • a raw material for the smooth layer (C) a crystalline homopolyester (1 Torr) dried at 135 ° C. for 6 hours under reduced pressure (1 Torr) M1) 60 parts by weight and 40 parts by weight of copolymerized polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours were mixed and supplied to the extruder 3 except that heat treatment was performed at 224 ° C. for 10 seconds.
  • the light diffusing polyester film of Example 5 was prepared by the same method as shown in Example 1.
  • Example 5 The properties of the film obtained in Example 5 are shown in Table 1. From Table 1, it can be seen that Example 5 has excellent characteristics as in Example 1.
  • Example 6 As raw materials for the light diffusion layer (B), 63 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. 34 parts by mass and 3 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2, and a crystalline homopolyester (1 Torr) dried at 135 ° C. under reduced pressure (1 Torr) for 6 hours as a raw material of the sliding layer (C) ( M1) 60 parts by mass and 40 parts by mass of copolymerized polyester (M2) dried under reduced pressure (1 Torr) for 12 hours at 70 ° C.
  • M1 crystalline homopolyester
  • M2 copolymer polyester
  • Example 2 The same method as shown in Example 1 except that after the transverse stretching, heat treatment was performed at 240 ° C. for 17 seconds, and a relaxation treatment of 1.3% was performed in the width direction in the process of cooling to 60 ° C. Conducted at 6 was to create a light-diffusing film of.
  • Example 5 has excellent characteristics as in Example 1.
  • Example 7 As raw materials for the light diffusion layer (B), 82.5 parts by mass of a crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and a copolymer polyester (1 Torr) dried at 70 ° C. for 12 hours (1 Torr) M2) 17 parts by mass and 1.5 parts by mass of acrylic-polystyrene crosslinked particles having a particle diameter of 4 ⁇ m were mixed and supplied to the extruder 2, and the layers (B), (A) and (C) A light diffusing polyester film of Example 7 was prepared in the same manner as shown in Example 4 except that the thickness ratio was 18:72:10.
  • Example 7 The characteristics of the film obtained in Example 7 are shown in Table 1. Although Example 7 was practically inferior in terms of optical characteristics with a low surface haze, excellent characteristics similar to Example 1 were obtained in terms of curl.
  • Example 8 As raw materials for the light diffusion layer (B), 78.7 parts by mass of crystalline homopolyester (M1) dried at 135 ° C. for 6 hours under reduced pressure (1 Torr), and copolymer polyester (1 Torr) dried at 70 ° C. for 12 hours under reduced pressure (1 Torr) M2) 21 parts by weight and 0.3 parts by weight of acrylic-polystyrene crosslinked particles having a particle diameter of 8 ⁇ m were mixed and supplied to the extruder 2, and the layers (B), (A) and (C) A light diffusing polyester film of Example 8 was prepared in the same manner as shown in Example 5 except that the thickness ratio was 9: 83: 6.
  • Example 8 The characteristics of the film obtained in Example 8 are shown in Table 1. In Example 8, although the total haze and the surface haze were low and practically inferior in terms of optical characteristics, excellent characteristics similar to those in Example 1 were obtained in terms of curling.
  • Example 9 As raw materials for the light diffusion layer (B), 62 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours.
  • the light diffusing polyester of Example 9 was prepared in the same manner as shown in Example 6 except that 37 parts by mass and 1 part by mass of silica particles having a particle diameter of 1 ⁇ m were mixed and supplied to the extruder 2. A film was created.
  • Example 9 The characteristics of the film obtained in Example 9 are shown in Table 1. In Example 9, although the total light transmittance was low and practically inferior in terms of optical characteristics, the same excellent characteristics as in Example 1 were obtained in terms of curl.
  • Comparative Example 1 As raw materials for the light diffusion layer (B), 74 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. 23 parts by mass and 3 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2. As a raw material for the smooth layer (C), a crystalline homopolyester (1 Torr) dried at 135 ° C. for 6 hours under reduced pressure (1 Torr) M1) 27 parts by mass and 73 parts by mass of copolymerized polyester (M2) dried under reduced pressure at 70 ° C.
  • M1 crystalline homopolyester
  • M2 copolymer polyester
  • Example 1 Comparative example using the same method as It was created of the light-diffusing polyester film.
  • Comparative Example 2 As raw materials for the light diffusion layer (B), 74 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. 23 parts by mass and 10 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2, a light diffusion layer (B) was provided instead of the smooth layer (C), and the layer (B) ( A light diffusion film of Comparative Example 2 was prepared in the same manner as shown in Example 1 except that the thickness ratio of the A) layer and the (B) layer was 11:78:11.
  • Comparative Example 3 As raw materials for the light diffusion layer (B), 74 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. 23 parts by mass and 3 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2, the smooth layer (C) was not provided, and the thickness ratio of the (B) layer and the (A) layer was 11 A light diffusion film of Comparative Example 3 was prepared in the same manner as shown in Example 1 except that the pair was 89.
  • M1 crystalline homopolyester
  • M2 copolymer polyester
  • Reference Comparative Example 1 As raw materials for the light diffusion layer (B), 58 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) for 12 hours at 70 ° C. 32 parts by mass and 10 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2, the smooth layer (C) was not provided, and the thickness ratio of the (B) layer to the (A) layer was 11
  • the method was the same as that shown in Example 1, except that a heat treatment was performed at 234 ° C. for 17 seconds and 3.3% relaxation treatment was performed in the width direction in the process of cooling to 60 ° C. Thus, a light diffusing film of Reference Comparative Example 1 was prepared.
  • Reference Comparative Example 2 As raw materials for the light diffusion layer (B), 51 parts by mass of crystalline homopolyester (M1) dried under reduced pressure (1 Torr) at 135 ° C. for 6 hours, and copolymer polyester (M2) dried under reduced pressure (1 Torr) at 70 ° C. for 12 hours. 46 parts by mass and 3 parts by mass of polystyrene (M3) were mixed and supplied to the extruder 2, and the drawing speed of the unstretched film by the cooling drum was adjusted so that the film thickness after stretching was 100 ⁇ m. After the smooth layer (C) was not provided, the thickness ratio of the (B) layer and the (A) layer was controlled to be 20 to 80, and the film was stretched 2.4 times in the width direction at 135 ° C.
  • M1 crystalline homopolyester
  • M2 copolymer polyester
  • Example 1 except that the film was stretched 1.6 times in the width direction at 140 ° C., further heat treated at 233 ° C. for 17 seconds, and subjected to 1.0% relaxation treatment in the width direction in the process of cooling to 60 ° C. Same as shown in It created a light-diffusing film of Comparative Reference Example 2 having a thickness of 100 ⁇ m by the method.
  • the light diffusing polyester film of the present invention can be used as a light diffusing film used in a backlight unit of a liquid crystal display, a lighting device or the like. Moreover, it can use as a base film for prism sheets. Therefore, it is important to contribute to the industry.

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Abstract

L'invention concerne un film de polyester diffusant la lumière qui possède une excellente résistance mécanique et un bon équilibre entre la transmittance de lumière totale et la diffusibilité de lumière. Le film de polyester diffusant la lumière ne s'enroule pas suite à un traitement à haute température. L'invention concerne plus précisément un film de polyester diffusant la lumière qui possède une structure en trois couches dans laquelle une couche de diffusion de lumière (B) est disposée sur une surface d'une couche intermédiaire (A) et une couche lisse (C) est disposée sur l'autre surface de la couche intermédiaire (A), ladite structure en trois couches étant obtenue par co-extrusion. La couche intermédiaire (A) se compose d'un homopolyester cristallin ou d'un polyester cristallin qui contient un composant de copolymérisation. La couche de diffusion de lumière (B) se compose de 50 à 99 parts en poids d'un polyester cristallin qui contient un composant de copolymérisation et qui possède un point de fusion de 225-255˚C, et de 1 à 50 parts en poids d'un additif qui est incompatible avec le polyester. La couche lisse (C) se compose d'un polyester cristallin qui contient un composant de copolymérisation et qui possède un point de fusion de 225-255˚C.
PCT/JP2010/069887 2009-11-20 2010-11-09 Film de polyester diffusant la lumière WO2011062081A1 (fr)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008003426A (ja) * 2006-06-23 2008-01-10 Nippon Zeon Co Ltd 偏光板
JP2009048156A (ja) * 2007-01-31 2009-03-05 Toyobo Co Ltd 表面光拡散性ポリエステルフィルム
JP2009186781A (ja) * 2008-02-06 2009-08-20 Mitsubishi Plastics Inc プリズムシート用ポリエステルフィルム

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008003426A (ja) * 2006-06-23 2008-01-10 Nippon Zeon Co Ltd 偏光板
JP2009048156A (ja) * 2007-01-31 2009-03-05 Toyobo Co Ltd 表面光拡散性ポリエステルフィルム
JP2009186781A (ja) * 2008-02-06 2009-08-20 Mitsubishi Plastics Inc プリズムシート用ポリエステルフィルム

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